Steps to reproduce:

1. Open Mozilla Thunderbird.
2. Open any email folder and go to list of email messages in that folder.
3. Switch to threaded view by checking in the main menu: View > Sort by > Threaded
4. Try pressing Control+Alt+Arrows to navigate this table.
5. Nothing happens - these keystrokes don't work.

Expected behavior:

You should be able to navigate by row or by column in this table.

Actual behavior:

Nothing happens. NVDA doesn't speak anything after pressing Control+Alt+Arrows. Sometimes Thunderbird switches view to the root of email account instead of the selected folder.

System configuration:

NVDA version:
Version: 2018.2

NVDA Installed or portable:
Installed

Other information:
I tried with and without "Mozilla app enhancements" add-on. This issue can be reproduced regardless whether this add-on is running or not.

Windows version:
Windows 10 Version 1803 Build 10.0.17134.112

Name and version of other software in use when reproducing the issue:
Mozilla Thunderbird Version 52.8.0 (32-bit)

Other questions:

Does the issue still occur after restarting your PC?
Yes

Have you tried any other versions of NVDA?
It was working correctly in 2018.1.1 and 2018.1.